1. Field of the Invention
This invention relates generally to pipe crawling apparatus, and more particularly to a robotic pipe crawling device capable of choosing its own path in a pipe maze.
2. Brief Description of the Prior Art
The efficient and safe operation of the underground natural gas piping system is a continuing concern of the gas utility industry. Methods presently used by gas companies to locate, inspect, and repair damaged or leaking buried gas pipes are for the most part imprecise, time consuming, and costly. The basic process involves locating the defective pipe and exact area of the pipe in need of maintenance, pavement removal, site excavation, pipe repair or replacement, and site restoration. Two major time, cost, and safety factors in this maintenance process are the difficulties in precisely locating the pipe and the specific pipe section in need of repair, and the potential for hazards and expenses to the utility and community from damaged or leaking pipe that goes undetected.
Equipment and techniques commonly used to locate these pipe leaks and defects includes electronic pipe locators, pipe tagging systems, combustible gas locators, and if such equipment does not provide the desired information, full excavation of the pipe. Even with the use of pipe and gas detectors, there is the possibility that after an excavator has uncovered a buried gas pipe to repair a leak, he may find that due to false detector readings, the section of exposed pipe is not leaking, or that the site of the excavation does not contain the pipe at all.
The potential danger from leaking underground gas pipe which escapes detection, and the cost to the gas industry for lost gas and unnecessary excavations, as well as excavations for the purposes of inspection, is significant. There is therefore a need to develop a system that could investigate the condition of underground gas mains and services from within the pipe, locate the exact position of both the pipe and the detected defect, and reduce the need for soil excavation and site restoration.
Self propelled devices which move through pipelines are known in the art. There are several patents which disclose self propelled devices of various constructions that are used inside pipelines.
Boucher, U.S. Patent No. 2,604,521 discloses a conduit tractor comprising a frame, three wheels arranged on opposite ends of the frame which are spaced uniformly apart about the longitudinal axis and a jack screw pantograph mechanism for adjusting one of the wheels relative to the axis. Two of the wheels are driven by an electric motor through a chain and sprocket arrangement.
Sigel-Gfeller, U.S. Pat. No. 4,112,850 discloses a conveyor apparatus having a driving chassis section and a driven chassis section with a pair of endless belts connecting the chassis sections and maintained in contact with the interior wall of the pipeline.
Vertut, U.S. Pat. No. 4,244,296 discloses a self-propelled vehicle with articulated arms having a body with at least one driving and guide wheel which bears on the pipeline interior surface and at least two pivoting arms articulated on the body and which have bearing members on the ends. The bearing members roll or slide on the surface opposite the guide wheel. The device also transmits a pivoting torque to the arms in such a way that the arms, by reaction, apply the driving wheel against the surface.
Okada et al, U.S. Pat. No. 4,526,106 discloses a motor driven vehicle comprising a pair of arms pivoted to each other at one pair of ends, a drive wheel coincident with the pivot, a swiveling wheel carried at the other end of each arm, and a spring positioned to pull the arms toward each other so that the dimension of the vehicle across the pipe is maximized.
Douglas, U.S. Pat. No. 4,537,136 discloses a pipeline vehicle having front and rear sets of wheels carried on sprung arms. Each wheel can be locked by a clutch. One set of wheels is locked while a ram is operated, causing the other set of wheels to roll forward. The main body of the vehicle can be rotated relative to the wheels by a motor operating via a drive belt. The interior of the body is pressurized with inert gas exhausted from the propulsion system which is vented by a one-way valve.
Okada et al, U.S. Pat. No. 4,563,954 discloses a motor driven vehicle comprising a pair of two-wheel trucks each pivotally connected to an end of a stretcher member which urges the trucks away from each other. Each truck has a driving wheel and a swiveling wheel.
Tolino et al, U.S. Patent discloses a portable and collapsible pipe crawler which includes a four-wheeled chassis with the sets of wheels along the opposite sides of the chassis being respectively driven by two hydraulic motors. A foldable mast pivotally connected to the chassis carries a pneumatic cylinder which forces bearing wheels against the opposite side of the pipe to force the chassis wheels into firm frictional engagement with the pipe interior. The chassis also carries a three-axis remote manipulator and one or two remotely controlled video cameras. A position indicator including a star wheel and proximity sensor is disposed for rolling engagement with the pipe to sense distance travelled.
The present invention is distinguished over the prior art in general, and these patents in particular by a robotic pipe crawling device having two three-wheel modules pivotally connected at each end of a chassis, with each module having one idler wheel and two driven wheels. Each module is formed of an idler yoke and a driveline yoke constructed of parallel laterally spaced rectangular side plates. The idler yoke is pinned at one end to the chassis and the idler wheel is rotatably mounted at the outer end. The driveline yoke is pinned intermediate its ends to the chassis and the drive wheels are rotatably mounted one at each end. A pivot motor at each end of the chassis pivots the wheeled modules independently into and out of a wheel engaging position on the interior surface of the pipe and a drive motor carried by the driveline yoke drives the two drive wheels in opposite directions to propel the device through the pipe interior. A second pivot motor mounted within each idler yoke allows the idler yokes to pivot independently of the driveline yokes. A swivel joint in the chassis midsection allows each end of the chassis to be rotated about the longitudinal axis relative to one another. The chassis may be extended by adding additional driveline yokes. In addition to a straight traverse the device is capable of executing a "role sequence" to change its orientation about its longitudinal axis, and "L", "T", and "Y" cornering sequences. Connected with a computer the device is capable of "learning" a series of axis control sequences after being driven through the maneuvers in a manually operated mode, thus choose its own path through pipe maze.